Enhanced bright peak clear phase shifting mask and method of use

Abstract

A clear phase shifting mask, particularly adapted to imaging nanostructures using X-ray lithography, includes a membrane having generally planar top and bottom surfaces the membrane being substantially transparent to the incoming radiation. In addition, the mask includes a pair of phase shift regions supported on the membrane, each of the regions defining a corresponding edge. During an imaging operation, the mask generates an aerial image defining, for each of the corresponding edges, an edge bright peak and an edge dark peak. By suitable choices of widths on the mask, the edge bright peaks can be caused to constructively interfere to form an enhanced intensity image bright peak. According to another embodiment, aphase shifting mask that images two-dimensional features on a target using the bright peak of the corresponding aerial image includes a membrane and a phase shifting material supported by the membrane. The phase shifting material defines an aperture that includes two pairs of opposed edges, each pair being separated by an associated perpendicular distance that is selected to facilitate constructive interference of the edge bright peaks to produce an enhanced intensity image bright peak that is used to image the two-dimensional feature.